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Phylum Arthropoda

Phylum Arthropoda. Terrestrial Mandibulates : Spiders and Insects. Characteristics. Segmented bodies Jointed appendages Specialized for eating, sensing, reproduction, defense and movement Exoskeleton Hard covering on the outside of the animal

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Phylum Arthropoda

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  1. Phylum Arthropoda Terrestrial Mandibulates: Spiders and Insects

  2. Characteristics • Segmented bodies • Jointed appendages • Specialized for eating, sensing, reproduction, defense and movement • Exoskeleton • Hard covering on the outside of the animal • Limits the growth of the organism (must shed) • Muscles are attached to this layer • Secreted by underlying epidermis • Shed (molted) at intervals

  3. Characteristics • Bilateral symmetry • Muscular system • Complex • Contains two types of muscles • Body cavity • Coelom is smaller in size   • Most of body cavity consists of hemocoel (sinuses, or spaces, in the tissues) • Filled with blood

  4. Characteristics • Digestion • Complete digestive system  • Esophagus, crop, gizzard, midgut, hindgut and anus • Mouthparts modified from appendages and adapted for different methods of feeding • Circulatory System • Open system • Dorsal contractile heart, arteries

  5. Characteristics • Respiration • Obtain oxygen through: • 1) body surface (diffusion), • 2) gills, • 3) tracheal (air tubes) – carry oxygen to muscles • 4) book lungs • Spiracles—small openings in the exoskeleton through which air opens

  6. Characteristics • Water retention—3 structures • 1) Malpighian tubules— • excretory structures that remove metabolic wastes from blood and return water to the cells • 2) Exoskeleton— • prevents water evaporation • 3) Book Lungs— • gas exchange without water loss (also used in respiration)

  7. Characteristics • Excretory system • Paired excretory glands in some • Same as the nephridial system of annelids  • Some with other excretory organs, called Malpighian tubules

  8. Characteristics • Nervous system • Contains same system of annelid (with dorsal brain connected by a double nerve chain) • Fusion of ganglia in some species   • Well-developed sensory organs • Compounds eyes with many lenses (can see motion and color)

  9. Characteristics • Reproduction • Sexes usually separate, • Paired reproductive organs and ducts;   • Usually internal fertilization; • often go through metamorphosis (change in body form  larva to adult)

  10. Classification • Phylum Arthropoda(most diverse phylum) • Subgroups of Terrestrial Arthropods: • Subphylum Chelicerata – • Characteristics of all: • six pairs of appendages that include • a pair of chelicerae, • a pair of pedipalps, and • 4 pairs of walking legs • No mandibles and no antennae.   • Suck up liquid food from their prey. • Two body segments (abdomen and cephalothorax)

  11. Classification • Class Merostomata– • Horseshoe crabs are practically unchanged • Have an unsegmented, horseshoe-shaped carapace, and a broad abdomen, which has a long spine like telson. • Book gills are exposed.   • They feed at night on worms and small mollusks and are harmless to humans. • Include horseshoe crabs

  12. Classification • Class Arachnida– • over 50,000 species • Body organization: cephalothorax, abdomen • Examples: Spiders (35,000 species), scorpions, ticks, mites

  13. Classification • Spiders: • hunt using strong legs and good eyes; weave silk for web (hunt and reproduction); fangs are modified chelicerae (liquefy prey with venom) • Scorpions: • long, segmented abdomen with a stinger; • Mites and Ticks: • mites have one body segment, eat bacteria or skin cells of humans; ticks are mostly parasitic, require blood before molting and can cause Rocky Mtn spotted fever

  14. Classification • Subphylum Uniramia– • Characteristics: • Appendages are unbranched.   • Includes the insects and the myriapods (centipedes and millipedes). • Heads resemble the crustacean head but have only one pair of antennae, instead of two. • Also have a tympanic membrane for sound  • Have mandibles and two pairs of maxillae • Respiration is by body surface and tracheal systems, • Although juveniles, if aquatic, may have gills.

  15. Classification • Class Chilopoda- • They are active predators with a preference for moist places such as under logs or stones, where they feed on earthworms, insects, etc.   • Each segment (they have between 10 and 70), except the one behind the head and the last two, bears one pair of appendages. • Include: centipedes

  16. Classification • Class Diplopoda– • Include Millipedes • Have cylindrical bodies made up of 25 to 100 segments. • Abdominal segments each have two pairs. • Millipedes are less active than centipedes • Generally herbivorous, living on decayed plant and animal matter

  17. Classification • Class Insecta– • Most numerous and diverse of all arthropods. • (There are more species of insects than species in all the other classes of animals combined!!) • Have three pairs of legs • Usually have two pairs of wings (although some have one pair of wings, or none)   • Body organization: head, thorax, and abdomen. • The head usually bears a pair of large compound eyes, a pair of antennae, and usually three ocelli.  

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